This invention relates to a magnetic rotor impeller assembly, and more particularly to such rotor assembly for use with an electromagnetic unit for drawing aquarium water into an aquarium for filtration of the contaminated aquarium water.
Aquarium filters are generally utilized for filtering and aerating aquarium water to maintain a clean environment for the fish in an aquarium tank and remove contaminated particles from the water. One type of aquarium filter is known as an external aquarium filter which hangs over the edge of the aquarium tank. An intake tube from the filter extends into the aquarium water. Water is drawn through the intake tube into a receiving chamber in the filter housing. The contaminated water then passes into a filtering chamber where the water circulates through filtering material which removes contaminating particles and debris from the water. The filtered water is then discharged from the filter housing back into the aquarium tank in a filtered and aerated condition.
In order to draw the water from the aquarium tank and pass it through the filter housing, there is typically utilized an impeller unit. The impeller is in the form of a pump which creates a reduced pressure at a location within the filter housing to cause water from the aquarium tank to be drawn into the filter housing. Such impeller is generally driven by a motor coupled to the filter housing.
In U.S. Pat. No. 4,512,885 there is described an external aquarium filter which includes a rotor magnetically coupled to an electromagnetic stator unit. An impeller is mounted with respect to the rotor for driving engagement by the rotor. In such aforementioned patent, the electromagnetic stator unit is removably coupled to the filter housing and includes a well hermetically separated from the stator stack. The rotor is part of an assembly which comprises a shaft which is fixed with respect to the stator unit. The rotor is rotatingly positioned on the shaft. A magnet is insert molded onto the rotor. The impeller is likewise rotatingly mounted onto the shaft and is operatively connected to be driven by the rotor. The electromagnetic stator unit creates a flux which is cut by the magnet to cause the rotor to rotate upon the shaft and drive the impeller. The impeller creates a reduced pressure which draws the aquarium water into the filter housing for filtration and aeration.
The rotor assembly in the aforementioned patent forms a single unitary assembly including the shaft, the rotor, the magnet mounted onto the rotor, and the impeller. A washer is mounted onto the shaft and plugs placed at opposing ends of the shaft to fix it in position with one end seated into the well and the other end fixed into an appropriate seat provided in the intake tube.
In manufacturing the rotor unit, a ceramic magnet was generally utilized and insert molded onto the rotor. In creating such ceramic magnet, the magnet would be molded, ground, and then insert molded onto the rotor unit, and then magnetized. The magnet being of ceramic material might suffer from shrinkage, might develop hairline cracks, and was costly both to manufacture and assemble. Nevertheless, such ceramic magnets were viewed to be the best type and most suitable for such purpose.